Compounding and vulcanization of synthetic rubber



Patented 7,1946

COMPOUNDING AND VULCANIZATIQN OF SYNTMTIC RUBBER Albert A. Somerville,Carmel, N. Y., assignor to R. T. Vanderbilt Company, Inc, New York,

N. Y., a corporation of New York No Drawing.

Application February it, 1944, Serial No. 522,785

24 Claims. (cl. 260-79l My invention relates to improvements in thecompounding and vulcanization or synthetic rubbers of the type producedby copol'ymerizatlon of substantial dimculties in the manufacture ofvol-- canized products from GR-S stocks. Even thouuh supposedlyidentical techniques and formulations are used by several producers,such synthetic rubber from one producer will, for example, exhibit agenerally higher rate of cure than that from others. But diflerentsamples item a single five ton lot from one producer will of cure. Thisvariability is a serious burden upon the production of vulcanizedproducts and inalso frequently exhibit markedly different rates 39valves the production of substantial quantities oi defective goods.Detects frequently appear,

{or example,- in inner tube sections adjacent value parts and inrelatively thick sections subjected to rapid curing as in rubber heelsas the result of such variability.

tion in rate of cure was so great as to submerge the variability in rateof cure ordinarily exhibited by GR-S rubber. When I attempted toreconcile these results with the reports which provoked my experiments,I found that the GR-S compounds which exhibited such curing failureswere sci-called sulfurless stocks. Continuing my experiments, with thisclue, I found that my new results were obtained with appropriateadditions of copper, as such or as an appropriate compound. in compoundsor GR-S rubber containing an amount of sulfur, as such, exceeding theamount required to form cupric sulfide with the copper present. Sulfurcombines with copper, to form cupric sulfide, in amount'about 50% byweight on the copper. The range of copper ditions with which my newresults were attained approximated 0.005-1% by weight on the GR-Srubber. With additions below the lower limit,

tained. With additions above 1%, the results began to resemble thoseincident to the addition of copper to natural rubber compounds. I alsotried the addition of copper to other t s of synthetic rubber but my newresults seemed to be peculiar to GR-S type'synthetic rubber. These newresults contradicted all my previous experilin studying the propertiesof GR-S stocks, I

addedrmeasured quantities'of metallic copper to a GR-S compound todetermine the precise effeet of copper in such compounds after I heardreports that GR-S stocks frequently tailed to cure when applied asinsulation in contact with cop per, for example in areas of defectivetinning when applied to tinned copper conductors as in conventionalpractice. Copper is rigorously exeluded from natural rubber compounds;copper seriously degrades vulcanized natural rubber the'vulcanization orthe GR-S stocks I used in my experiments without adversely aflectlnztheir ence with other rubbers.

The following examples will illustrate practices embodying mylnventionand include comparisons indicating some 0! its advantages. thetabulaticnsof these compounds, cures and physical properties. thecompound of each example was made up of the number of parts by weightindicated opposite each designated component, the cures were in a platenpress for the periods indicated in minutes at the left under the curingtemperature, all of the cures in each group being eflectedat the sametemperature, and, for .each period of cure, thevalues for stress at 300%elongation in pounds per square inch appear un- 1 der "S," for tensilestrength in pounds per square '1 inch under "'1'" and for percentageelongation at properties with respect to ageing. The accelera- 46',break under E."

0.005%, my new results were notregularly at- Example I Example 11Example 111 Example IV GR-S rubber 100 100 100 100 Plastlclmr 5 5 5 Zincox e 5 5 5 5 Channel carbon black 50 50 50 50 ullur 2 2 2 2Benmthlazg 1. 5 1. 5 1. 5 1. 5 Zinc diethy qithiocarbam 15 15 15 15Powdered copper 10 1 BEFORE AGEING 307 F. S T E S '1 E S lomlnutes 275910 745 1130 2280 445 1070 2800 540 830. 2580 30 minutes AFTER 24 HOURSIN H OT AIR OVEN AT 250 F.

10 minutes- 1030 150 1210 1220 1380 130 mmlnnmq 1%!) 110 1320 105 1340130 ZOminutes mo 1490 1360 1520 150 30 minutes 1450 1640 1450 1640 SHOREHARDNEBB BEFORE AGEING 10 minutes 77 81 81 80 15 minutes 80 81 80 80 20minutes.. 80 81 80 80 30 minutes 80 81 80 80 The foregoing Examples I toIV illustrate screen. The acceleration in rate of cure will be theresults or my first experiments with copper apparent from a. comparisonof the physical propin GR-S rubber. The copper used waselecertiesparticularly for the 10 and 15 minute trolytic copper passing a 300 meshper inch cures.

Example V Example VI. Example VII Example VIII g? GR-B rubber. 100 100100 100 4 100 P 5 5 5 5 5 Zine oxide. 5 5 5 5 5 Ch 50 50 50 50 50 S 2 22 2 2 Benzothlu dlsulphl 5 5 1. 5 1. 5 1. 5 Zinc diethy thiocarbamate 1515 15 .15 15 Powdered copper .5 1 3 5 BEFORE AGEING 520 510 UncuredUncured Uncured 1515 550 270 535 620 Uncurerl Uncured 2470 490 775 2340610 275 435 580 Uncured 2300 615 Uncured 2100 345 1690 2410 385 585 1930630 Uncured Example x Example XI Example XII Example XIII 100 100 100100 5 5 5 5 5 5 5 5 50 50 50 50 2 a 2 2 1.5 1. 5 1. 5 1. 5 15 15 15 15Powdu'ed eoppc.............. .10 .01 .005 .001

$7 I. B '1 E B T E S T E 8 T E 1125 515 Uncured Uncured Uncured m5 415740 610 565 1300 670 2355 1140 2475 1055 2575 545 705 2400 610 2000 3151365 2375 415 1290 400 1025 2100 470 235 840 1710 370 1695 2110 360 1450435 The foregoing Examples V to XIII illustrate the effect of variationsin the amount or added coper. Again the copper used was electrolyticcopper passing a 300 mesh screen. Useful results were secured withtheaddition of copper in amps? The foregoing Examples XIV to XVIillustrate the advantaie oi thorough dispersion or the copper.Dispersion may be accomplished by using finely divided copper, as inExamples II-IV, VI-XIII and XV or by using copper compounds amountsranging from about 0.005% to about 1% soluble or partially soluble inthe rubber or by on the GR-S-rubber. I have secured optimum using-coppercompounds predispersed in or upon results with the addition oi copper inamounts some appropriate compounding material. For ranging from about0.1% toabout 0.5% on the example, copper compounds may be dispersed GR-Srubber. It will be noted that the sulfur upon inert fillers or they maybe dissolved or dis exceeds 50% by weight'on thecopper in each or persedin-plasticizers such as mineral oils, coal the foregoing examples otherthan the blank, tariractions, and esters such as dibutylphthalate.Example V, and the example using 5 parts of In general, the copperaddition may be made to copper. Notwithstanding the excess of sulfur thecopolymer of butadiene and styrene, before or used in Exampl VIII,the'resuits are unsatisduring compounding, or it may be made to anyfactory with as much as 3 parts or copper. I compounding materialwithwhich it is compatihave examined sections or vulcanizates of Exbleand'thus incorporated in the-synthetic rubber amples VI. VII, X, xIandXII under a microcompound with the modified compounding scope at 100magnifications and these appear, material. p

Example XVII Example XVIII. Example!!! ExompleXX Example XXI 100 100 loo100 100 s s s s s 6 5 6 6 6 so so so so to ur 2 2 2 2 2Bensothiasyldisuiphide i. ll 1. 5 1. d l. l i. 5 Zincdiethyldithlocarbamate. 16 ll l6 I8 15 Copper powder (through 300 mesh)10 835g; alga (anhydrous) u 2 5 N Coppercarbona n II'" "fiii Barons:AGEING,

sor'r s'rns'rns'rss'rss'rn o sosssosoosoomsossossomsoomm'mo svsssonoommeosnsosaonsomo mimmomuumm eas mo use use mo s use mo sso lsioalso in use was ass mmosaomaommisaomoaoissoassoarsimaoao-aisissommmmmosssmoamsasmmoalsmomsomo arms 24 nouns in nor am OVEN n w rfiminuizes mo loo moo so use 10s non mi 10 minutes '1110 no use as moios mo 11o use no "minutes 1810 110 1870 Ill. 14!) 1U IN 106 1570 115mmlnutem mo no mo no use us mo ns use no 30mlnutcs mo us 1440 no me nouse no nao 125 thus examined, to'containdispe'rsed particles of 1 copperwith surfaces darkened as by a iilm of the eitectiveness ot a variety orcopper compounds. The amounts of the several compounds used in ExamplesXIJQXX and III are such that the copper. measured as copper. P sapproximates that in Example XVIII. The copper compounds I have triedwhich produce comparable results, in terms or the amount or coppermeasured as copper thus added to the GR-B rubber, include coppersulfide, cuprous oxide, an-

hydrous copper sulfate, copper sulfate with water otcmtallixatiomeoppercarbonatacoppernitrate, copper acetate, cuprous chloride. cupricchloride, copper oleate. and copper 'stearate. In fact the, only coppercompound I have tried which failed to give my new results, usedinappropriate amounts corresponding to their equivalents as sulfide.

Exam le Example Exam XI? X XV? GR-B rubber 100' 100 Plasticirer 0 6 6Zinc oxide 6 d 6 Channel carbon black 50 d0 50' Sulinr 2 2 2Bensothiazyldlslflphlde....; I. 5 1.6 l. 15 Zinc diethyldithlocarbamatel5 15 15 Copper gowder through {mo-mes screen l Copper powder through40-mesh screen 1 5 minutes.- Uncnred 245 500 475 Uncured 10 minutes 810696 mo mo 48) 51 1840 0B0 15 minutes.. moo 101) 2100 8 10m moo 51020mlnutes soozssosssmomo soomomosso 30 mlnutesn." 1m 27404 100 2611 8150use 228) 380 copper. is cuprlcoxide. I have no explanation for thisanomaly, but the following examples XXII to XXV will illustrate myfindings.

tin, tungsten and zinc. Copper appears to be unique.

Example XXIII Example XXIV Example XXV 100 100 100 5 5 5 5 5 5 50 50 502 2 2 1.5 1. 5 1. 5 .11 1 16 Cnpric oxide 125 Cuprous oxide 115 Theinvention includes the use of metallic copper and equivalent weights ofcompounds of copper, particularly salts including soaps of copper andcuprous oxide, but excludes the use oi cupric l The plasticizer used inthe foregoing examples was a mixture of 15 parts by weight of apetroleum sulionate, 5 parts of normal butyl alcohol and 80 parts of aviscous petroleum oil (currently oxide. 1 disclaim cupric oxide as acompound sold under the trade-name Reogen").

of copper embodying my invention.

In carrying out my invention the copper, or

Example XXVI Example XXVII Example XXVHL Example X XIX Example XXX(112-8 rubber 100 100 1 100 100 Plasticizer 5 5 g 5 6 Zinc oxide 5 5 5 55 Channel carbon black 50 50 50 Benxothiax ldkulphide--. 1. 5 1. 5 1.5 1. 5 l. 5 Zinc diethy dithlocarbama l5 15 15 15 l6 Suliuir 2 2 2 2 2Powered copper- .1 Powered iron"... 1 Powrered mangan l Pow' er .1

BEFORE AGEING ao7 F. s 'r E s '1 E s 'r a s 'r E s T E 695 1010 2440 525320 108) 725 370 1400 705 see 1270 545 The foregoing Examples XXVIII tom illus- I hate the results secured with other metals. The

metals used, including the copper in Example XXVII, passed a 800 meshscreen. Iron was the only metal showing any marked improvement,

erties only in the longer cures, 20 and 30 minutes, lacking theaccelerating eil'ect of copper. The metals I have tried. withoutapproaching my new results with copper, include aluminum, antimony,bismuth, cadmium, chromium, iron, lead,

manganese, molybdenum, nickel, silicon, silver,

' and it was eflective in improving physical propits equivalentcompound, may be incorporated in I 0.005-1% or better about 0.01-0.5% byweight 01' copper on the copolymer. My invention also includes thevulcanizable but unvulcanized oo- 75 polymer containing about 0.005-1%or better about 0.01-0.5% by weight of copper on the copolymer andupwards of about 50% by weight on the copper of sulfur and the productof vulcanization of such copolymers containing copper and sulfur. Theproportion of sulfur used is not critical and may follow conventionalpractices providing it is added to the compound subjected tovulcanization in, amount exceeding that required to combine with theadded copper to form cupric sulfide,

I claim:

1. A rubbery copolymer of butadiene and styrene containing as a sulphurvulcanization accelerator about 0.005-1% (calculated as copper) byweight on the copolymer of a material of the class consistingof metalliccopper and compounds of.

copper effective to accelerate the sulphur vulcanization of thecopolymer.

erator about OBOE-1%- by'weight on the copoly- ,met or metallic copper.

1s. The product oivulcanization of a rubbery copolymer of butadiene andstyrene'containing about 0.005-1% (calculated as copper) by weight onthe copolymer of a material of the class con- 3; A rubbery copolymer ofbutadiene and styrene containing as a sulphur vulcanization acceleratorabout 0.005-1% (calculated as copper) by weight on the copolymer of a;salt of copper.

4. A rubbery copolymer of butadiene and styv 14. The product ofvulcanization of'a rubbery copolymer ofbutadien'e and styrene containingabout 0.005-1%'by weight on the copolymer oi metallic copper and inexcess of by weight on the copper of sulfur.

15. The product of vulcanization of a rubbery copolymer of butadiene'andstyrene containing about 0.00 5-1% (calculated as copper) by weight onthe copolymerof a salt of copper and in excess of 50% by weight on thecopper of sulfur.

16. The product of vulcanization of a robbery copolymer of butadiene andstyrene containing about 0005-172, (calculated as copper) by weight onthe copolymer of cuprous-oxide and in excess of 50% by weight on thecopper of, sulfur.

17. A rubbery copolymer of butadiene and sty-.- rene containing about0.01-0.5% (calculated as copper) by weight on the copolymeroi 'amaterial of the class consisting of metallic copper and r'enecontainingas a sulphur vulcanization accelrene containing about.0.005-1%(calculated as compounds of copper effective to accelerate thevulcanization of the copolymer'and'in excess of 50% by weight on thecopper of sulifuri' .18. A rubbery copolymer of butadiene and styrenecontaining about 0.01-0.5% by weight on the copper) by weight on thecopolymer of a material of the class consisting of metallic copper andcompounds. oi copper effective to'accelerate the vulcanization of thecopolymer and in excess 0 50% by weight on the copper of sulfur.

l 6. A rubbery copolymer of butadiene and sty- 7 rene containing about0.0051% by weight on the copolymer of metallic copper and in excess of50% by weight on the copper of sulfur;

7. .A rubbery copolymer orbutadlene and styfrenecontaining about0l005-1% (calculated as copper) by weight on the, copolymer 01" a saltoi copper and in excess oi 50% by weight on the copper of sulfur.

copperoi sulfur. Y c

9. A rubbery copolymer oibutadiene and styrenc containing as a sulphurvulcanization accelerai'or abouti).01-0.5% (calculated as copper) byweight on the copolymer of'a material of the 7 class consisting ofmetallic copper and compounds or copper eiifective to accelerate thesulphur vulcanization of the copolymer. r

' 10. A rubbery copolymer of butadiene and styrenecontaining as asulphur vulcanization accelrene containing about 0.01

copolymer of metallic copper and in excess of 50% by weight on thecopper of sulfur.

19. A rubbery copolymer of butadiene and styrenecontaining about0.01-0.5% (calculated as lymer oi a salt of copper) by weight on the cccopper and inv excess 01' 50 q by weight on the copper of sulfur.

- 20. Arubbery copolymer 0 butadiene and stycopper) by weight on thecopolymer of'cuprous oxide and in excess of 50% by weight on the cop perofsulfur. c -21. The productot vulcanization of a-rubbery copolymer ofbutadiene andistyrene containing about 0.01-0.5% (calculated as copper)by weight on the copolymer of a material of the classccnsisting ofmetallic c'opperand' compounds of copper efiective to acceleratethevulcanization of the copolymer and in excess of 50%by weight on thecopper'o! sulfur.

22. The product of vulcanization of a rubbery copolymer of butadiene andstyrene containing "about 0.01-0.5% by weight on the copolymer ofmetallic copper and in. excess of 50% by weight on the copper ofsuliur.

orator about 0.01 0.5% by weight on the copoly-.

mer oi metallic copper.-

11. A rubbery copolymer'oi'buta'diene arid Sty- I rene containing as asulphur vulcanization accelcrater about 0.01-0.5% .(calcula'tedascopper) by weight on the copolymer of a salt of copper.

12. A rubbery copolymer ofbutadiene and sty- 7 5 l containing as asulphur vulcanization accelorator about 0.01-0.5% (calculated as copper)by weight on the copolymer of cuprous oxide. 4

.23. The product or vulcanization oi'a rubbery copolymer of butadieneand styrene containing about 0.01-0.5% (calculated as copper) by weighton the-copolymer of a-saltof copper and in excess of 50% by weight onthe copper of sulfur.

on the copolymer of cuprous'oxide and in excessor 50% by weight n thecopper oi sulfur.

.5% (calculated as Y ALBERTA. somnavrnm.

